Gas turbine engines generally include a turbine section downstream of a combustion section that is rotatable with a compressor section to rotate and operate the gas turbine engine to generate power, such as propulsive thrust. General gas turbine engine design criteria often include conflicting criteria that must be balanced or compromised, including increasing fuel efficiency, operational efficiency, and/or power output while maintaining or reducing weight, part count, and/or packaging (i.e. axial and/or radial dimensions of the engine).
Known conventional and interdigitated gas turbine engines generally include labyrinth seals between rotating and static members of a turbine section. Air generally needs to be sealed within cavities to avoid excessive leakage into the core flowpath. Furthermore, for turbine sections including rotating outer drums or shrouds, relative closures or clearances between rotor and stator assemblies vary. For example, labyrinth seals generally have leakage rates per unit diameter rise as diameter is increased, thereby rendering labyrinth seals increasing inefficient at rotating outer drum to static case interfaces. As such, known labyrinth seal assemblies may result in leakages that may obviate efficiencies created by interdigitated turbine sections.
Furthermore, known seal assemblies may include abradable structures designed to allow or tolerate a rub of a rotor seal against a static structure, such as a shroud, at various thermal conditions and rotational speeds. However, as the engine operates and rubs the static structure, over time the effectiveness of the seal assembly degrades, thereby reducing turbine performance and efficiency that may obviate the efficiencies of an interdigitated turbine section.
As such, there is a need for a seal assembly for an interdigitated turbine section of a gas turbine engine that may tolerate large axial and radial shifts of the rotor assembly relative to the static structure or frame. Furthermore, there is a need for a seal assembly that provides little or no deterioration over time.